Method for manufacture of bearings

ABSTRACT

A process for manufacturing an unground bearing suitable for high-speed applications comprises forming a subassembly including the inner race, balls, and retainer; the subassembly being fabricated in a fixture which receives the balls from a standard ball feeding machine. The subassembly is, after completion, removed from the fixture and positioned in one of the halves of a split outer race, the other half of the split outer race is placed over the subassembly and an outer shell is thereafter crimped over the outer races to hold the bearing together.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to the manufacture of bearings andparticularly to the assembly of unground bearings suitable forhigh-speed applications. More specifically, this invention is directedto the fabrication of bearings characterized by a split outer race and aball retainer and the invention further comprises tooling for use in theproduction of a subassembly consisting of the bearing inner race,retainer and balls. Accordingly, the general objects of the presentinvention are to provide novel and improved methods and apparatus ofsuch character.

(2) Description of the Prior Art

In the prior art a distinction has been made between comparativelyexpensive precision or "ground" bearings and relatively inexpensive"unground" bearings. An "unground" bearing, which is characterized by anouter race which is stamped rather than being precision machined, hasnot previously been considered to be suitable for high-speedapplications and particularly for use where a significant level ofbearing noise would be objectionable. A "ground" bearing, by virtue ofits utilization of a precision machined outer race, is expensive becauseof the time consuming nature of the procedures incident to the assemblythereof and because of the added costs incident to the machining of theouter race. Both "ground" and "unground" bearings, and the method bywhich they are assembled, are well known in the art and will not bediscussed herein. Suffice it to state that there has been a long feltneed for a bearing having the capability of operation at comparativelyhigh speeds with low noise which bearing could be assembled withmoderate labor costs when compared to prior art "ground" bearingassembly techniques.

SUMMARY OF THE INVENTION

The present invention overcomes the above briefly discussed deficienciesof the prior art by providing a novel technique for the assembly ofunground bearing suitable for high-speed applications. The presentinvention also contemplates unique tooling for use in the assembly ofunground bearings.

A bearing manufactured in accordance with the present invention ischaracterized by a split outer race and a ball retainer. Ground bearingspreviously produced commercially have included a retainer but have notemployed a split outer race. Previously available unground bearingshave, in some instances, employed a split outer race but have notincorporated a retainer; i.e., the space between the inner and outerraces of previous unground bearings has been filled with balls asopposed to having a partial complement of balls and a retainer.

In accordance with the present invention, a subassembly consisting of amachined inner race, the balls and a metal or plastic retainer is formedin a fixture. The fixture has a novel design which permits the balls tobe delivered thereto from a standard ball feeding device; the fixturedirecting the balls into precisely the proper relative positions wherethey are in contact with the ball track; i.e., the raceway; of the innerrace and are prevented from moving in a circumferential direction.Thereafter, the retainer is pressed into position to capture the balls.The inner race-ball-retainer subassembly, which may be handled, isthereafter positioned in a first half of the split outer race, thesecond half of the split outer race is placed over the subassembly andthe entire bearing is completed by securing the halves of the splitouter race.

BRIEF DESCRIPTION OF THE DRAWING

The present invention may be better understood and its numerous objectsand advantages will become apparent to those skilled in the art byreference to the accompanying drawing wherein like reference numeralsrefer to like elements in the several figures and in which:

FIG. 1 is a flow diagram which depicts the assembly of a high-speedunground bearing in accordance with the present invention;

FIG. 2A is a cross-sectional, side elevation view of a novel tool foruse in formation of a bearing subassembly in accordance with the processof FIG. 1;

FIG. 2B is a top view, with the ball feeding device partly broken away,of the novel fixture of the tool of FIG. 2A; and

FIG. 3 is a perspective view of a bearing subassembly A produced inaccordance with the method of FIG. 1 and employing the tooling of FIGS.2A and 2B.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to the drawing, the components of a bearing producedin accordance with the present invention are individually fabricated byconventional manufacturing techniques. Thus, the balls 10 (see FIGS. 2and 3) are formed by means of a conventional repetitive grinding processindicated at 10A in FIG. 1. The inner race defining member 12 willtypically be formed by a process which includes machining the part andhardening the finished part. Formation of the inner race defining member12 may also include a roller burnishing step to achieve the desiredfinish. The step of fabrication of the inner race is indicated at 12A.The halves of the outer race, one of which is depicted in perspectiveand partial cross-section at 14 in FIG. 1, will be produced from a stripof material by means of a process which includes the steps of blanking adisc from the strip, punching a hole in the disc and thereafter formingthe part into the requisite half-race shape which may be seen fromFIG. 1. The formation of the outer race segments includes swaging andcoining operations which will give the desired radius and finish to theparts whereby they will possess the same finish characteristics as theinner race. Subsequent to forming, the outer race segments will behardened. The formation of the outer race has been indicated in FIG. 1as step 14A. A "soft" outer shell 16, also shown in perspective in FIG.1, is formed in step 16A by a stamping procedure. For the reason to beexplained below, shell will be over-sized so that the outer racesegments 14 fit loosely therein. The retainer, an example of which isindicated in FIG. 3 at 18, may be formed from a suitable plastic, asindicated at step 18A, by a technique such as injection molding.

The assembly of a bearing in accordance with the process of FIG. 1contemplates the "simultaneous" formation of subassemblies. Thus, asindicated at step 20, one of the outer race defining members 14 will beplaced in an outer shell 16 to form a subassembly B. This subassembly Bwill then be positioned to receive a subassembly A assembled in themanner to be described below.

The inner race 12 is positioned, as shown in FIG. 2A, in a fixture whichhas been indicated generally at 22; the step of placing the inner racein the fixture being indicated in FIG. 1 at 22A. The fixture 22 will bedescribed in greater detail below. After positioning the inner race 12in the fixture, the requisite number of balls 10 are delivered theretoand, because of the design of the fixture, the balls will drop intopositions wherein they contact the ball track of the inner race and areprevented from circumferential movement. The step of delivering theballs to fixture 22 has been indicated at 24 in FIG. 1. Thereafter,subassembly A is completed, thus producing the article indicatedgenerally at 26 in FIG. 3, by urging the plastic retainer 18 over theballs as indicated at step 26A. The retainer 18 will, due to its shapeand resiliency, snap into position over the balls which have beencaptured in the appropriate positions in fixture 22; the balls thusbeing prevented from radial movement and from relative circumferentialmovement by the retainer and the retainer and balls being held in theball track of the inner race.

After subassembly A; i.e., the article 26 shown in FIG. 3; is completed,it will be ejected from the fixture 22 and placed within the subassemblyB wherein the balls will be in contact with one of the halves 14 of theouter race. The mating of subassemblies A and B, to form a furthersubassembly C, is indicated in FIG. 1 at 30. The assembly of the bearingis completed by dropping a second outer race defining member 14 oversubassembly C, as indicated at step 32, and thereafter forming the outershell 16 about this second outer race defining member, as indicated atstep 34, to hold the outer race together. The step of forming the shellover the outer race includes shrinking the shell to align the outer racedefining members and crimping the open end of the shell inwardly. Thisprocedure will cause the halves 14 of the outer race to be in peripheralabutting relationship at their maximum inner diameters. It is to beunderstood that techniques other than employment of an outer shell maybe utilized to position and hold the outer race halves with respect tosubassembly 26 and to each other (FIG. 3).

Referring again to FIG. 2A, and also simultaneously to FIG. 2B, thefixture 22 is provided with a cylindrical central bore having portions44 and 46 of different diameter joined by a frustoconical shapedintermediate section 48. The inner race 12 is dropped into the largerdiameter end 44 of the bore in fixture 22 and will be centered by theconical intermediate wall section 48. The inner race 12 will, whenseated in fixture 22, be supported on the reciprocal plunger 40 of anejector mechanism which operates through the smaller diameter portion 46of the bore in fixture 22. The walls of the larger diameter cylindricalportion 44 and the intermediate section 48 of the bore in fixture 22 aremachined to define spaced "pockets" commensurate in number with thenumber of balls to be included in the bearing. These "pockets", whichare open to the bore in the fixture and have axes which are parallel tothe axis of the fixture bore, are characterized by straightsemi-cylindrical vertical walls which converge inwardly toward the base;the converging portions of the walls of the pockets having a doubleconical shape in the disclosed embodiment. For example, from the lowerend of the vertical wall portion, the walls of the "pockets" may firstslope inwardly at an angle of 30°, as indicated at 50 in FIG. 2B, andthereafter slope inwardly at an angle of 45° with respect to thevertical, as indicated at 52. The size and shape of the "pockets" in theside wall of the bore in fixture 22 will permit the balls 10 to clearthe race defining upper land on inner race defining member 12 and, oncebelow the upper land or shoulder, the balls will be guided downwardlyand inwardly against the raceway and the flat bottom portion 54 of the"pockets". The pockets may be formed employing an end mill with a doubletaper and a flat tip. The balls are delivered to fixture 22 by means ofa standard ball feeding device which has been indicated schematically at36; the ball feeding device 36 including a mechanism such as a slidingdoor 38 which releases the requisite number of balls into fixture 22from positions generally aligned vertically with the above-described"pockets".

Once the balls have been released into the fixture 22, registrationbetween the ball feeding device 36 and fixture 22 is terminated and theretainer 18 is placed in the fixture and snapped into position over theballs. This operation can be performed manually or automatically.Thereafter, the plunger 40 is employed to eject the subassembly 26 fromfixture 22 and the process will be repeated to form subsequent innerrace-ball-retainer subassemblies.

While a preferred embodiment has been shown and described, variousmodifications and substitutions may be made thereto without departingfrom the spirit and scope of the invention. Accordingly, it is to beunderstood that the present invention has been described by way ofillustration not limitation.

What is claimed is:
 1. Apparatus for use in the fabrication of a bearingcomprising:means defining a bore having an axis, said bore having anupper portion with a minimum diameter selected to be larger than themaximum outer diameter of a bearing inner raceway defining member, saidbore having a second portion which converges inwardly toward said axisfrom a first end of said upper portion to a diameter smaller than saidmaximum outer diameter of the bearing inner raceway defining member; anda plurality of spaced recesses formed in the wall of said bore of saidbore defining member, said recesses having axes which are parallel tothe axis of the bore, said recesses each having an upper section whichextends downwardly from the second end of said bore defining means upperportion and a second section which extends generally downwardly andinwardly from said upper section, said second sections of said recessesterminating in flat bottoms, said recesses each having a size and shapesufficient to guide balls delivered thereto past the raceway definingupper land of an inner raceway defining member supported in said boresecond portion and thereafter inwardly into contact with the racewaysurface.
 2. The apparatus of claim 1 further comprising:means forejecting bearing subassemblies from the bore of said bore definingmeans.
 3. Apparatus for use in fabrication of a bearing comprising:meansdefining a bore having an axis, said axis of said bore being verticallyoriented, said bore having an upper portion with a minimum diameterselected to be larger than the maximum outer diameter of a bearing innerraceway defining member, said bore having a second portion whichconverges inwardly toward said axis from a first end of said upperportion to a diameter smaller than the said maximum outer diameter ofthe bearing inner raceway defining member; and a plurality of spacedrecesses formed in the wall of said bore of said bore defining member,said recesses having axis which are parallel to the axis of the bore,said recesses each having an upper section which extends downwardly fromthe second end of said bore defining means upper portion and a secondsection which extends generally downwardly and inwardly from said uppersection, said second sections of said recesses having a double conicalshape whereby the balls are directed downwardly and inwardly at a firstangle and then at a second lesser angle with respect to a horizontalplane through the vertical axis of said bore, said recesses each havinga size and shape sufficient to guide balls delivered thereto past theraceway defining upper land of an inner raceway defining membersupported in said bore second portion and thereafter inwardly intocontact with the raceway surface.
 4. The apparatus of claim 2 whereinthe second portions of said recesses terminate in flat bottoms.
 5. Theapparatus of claim 4 further comprising:means for ejecting bearingsubassemblies from the bore of said bore defining means.
 6. Theapparatus of claim 5 further comprising:means for delivering balls toeach of said recesses.